Calculating Amps and VA for Multiple Secondary Windings in a 28W Transformer

But if i only give $5 to one of them and $6 to another, someone is going to be unhappy.In summary, the conversation discusses a transformer with multiple primary and secondary windings and a power consumption of 28 watts. The speaker is seeking help in determining how to calculate the total VA and wire gauge for the transformer. The expert summarizer explains that the power output is dependent on the load and the wire sizes used, and that the primary current will be slightly higher than the calculated value. Additionally, the expert clarifies that the 28 watts must be shared among all secondary windings, and that each winding must be able to handle the amount of current required.
  • #1
Divendra Nath
I have a transformer that has 120/240 on the primary,but the secondary has multi volt ,33v 0v,13.5v 0v,2.7v 0v 2.7v,9v 0v 9v.The power consumption is 28watts only.How you work out 28watts with all secondary windings to find amps so I can calculate for total VA,and wire gauge?.Some one out there is and has that knowledge to show me the right way to do this please.
 
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  • #2
Divendra Nath said:
I have a transformer that has 120/240 on the primary,but the secondary has multi volt ,33v 0v,13.5v 0v,2.7v 0v 2.7v,9v 0v 9v.The power consumption is 28watts only.How you work out 28watts with all secondary windings to find amps so I can calculate for total VA,and wire gauge?.Some one out there is and has that knowledge to show me the right way to do this please.
It depends on what current you are drawing from what output voltage. If you consume all 28 watts out of the 2.7v output, you'll get a very different current than if you consume all 28 watts out of the 33v output.
 
  • #3
Thankyou for your kind response.So how it can be achieved .Do I have to share that 28watts with all secondary.So if I use 28watts with one winding it will be loaded and I can't use it with others.How should I do this?.
 
  • #4
Divendra Nath said:
Thankyou for your kind response.So how it can be achieved .Do I have to share that 28watts with all secondary.So if I use 28watts with one winding it will be loaded and I can't use it with others.How should I do this?.
I have no idea what your load is going to be so have no possible answer for you.
 
  • #5
Divendra Nath said:
So how it can be achieved .Do I have to share that 28watts with all secondary.So if I use 28watts with one winding it will be loaded and I can't use it with others.
Correct.

A transformer transfers power between windings through a magnetic field. The total power a transformer can handle is determined by the material and the physical size of both the core and of the wire used in the windings. Different core materials can support different strengths of magnetic field for a given size.

The wire sizes used will determine how much current they can carry before they overheat and burn the insulation, or even melt.

WATTS is the product of VOLTS times AMPS. W = V x A. So if you know any two of them you can find the third one.

In your example if you draw 28W from the 33V winding the current thru that winding will be W/V = A, or 28/33 = 0.85A. If you draw 28W from a 2.7V winding the current there would be W/V = A, or 28/2.7 = 10.4A.

In both cases the primary current (in a perfect transformer) will be W/V = A, or 28/240 = 0.12A. Since no one has come up with a perfect transformer yet, the primary current will be a little bit higher; around 10% to 20% higher is common for small transformers.
 
  • #6
Divendra Nath said:
Do I have to share that 28watts with all secondary

Yes.
You can put 28 watts into the primary and apportion it to the secondaries as you see fit, provided each secondary is capable of handling 28 watts worth of current by itself.

Just like paying my monthly bills - if i have $28 available and i have four creditors, i can give $7 to each of them or divide it between them according to my whim.
 
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Likes Tom.G

1. How do you calculate the amps for multiple secondary windings in a 28W transformer?

To calculate the amps for multiple secondary windings in a 28W transformer, you will need to know the total wattage of the transformer and the voltage of each secondary winding. You can then use the formula I = P/V, where I is the current (amps), P is the power (watts), and V is the voltage. For example, if the transformer has 3 secondary windings and each has a voltage of 12V, the total wattage would be 24W (3 x 12). Using the formula, the total amps would be 1.17A (28/24).

2. What is the difference between amps and VA in a transformer?

Amps (A) and VA (volt-amps) are both units of measurement for electrical current. However, amps refer to the actual amount of current flowing through a circuit, while VA refers to the apparent power of a circuit. VA takes into account both the current and the voltage in a circuit, while amps only measure the current. In a transformer, the VA rating is typically higher than the amps rating, as it accounts for the reactive power used by the transformer.

3. Can a transformer have different secondary windings with different amps and VA ratings?

Yes, a transformer can have multiple secondary windings with different amps and VA ratings. This allows for different levels of voltage to be produced for different applications. For example, a transformer may have one secondary winding with a higher amps rating for powering larger devices, and another secondary winding with a lower amps rating for powering smaller devices.

4. How do you determine the total VA rating for a transformer with multiple secondary windings?

The total VA rating for a transformer with multiple secondary windings can be determined by adding together the individual VA ratings of each secondary winding. For example, if a transformer has two secondary windings with VA ratings of 10VA and 15VA, the total VA rating would be 25VA.

5. Can you use the same formula for calculating amps and VA for transformers with different wattages?

Yes, the formula I = P/V can be used to calculate both the amps and VA for transformers with different wattages. The only difference would be the value used for P, which would be the total wattage of the transformer in the case of VA, and the wattage of the individual secondary winding in the case of amps.

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